Nested Card inside Accordion's `body` missing bottom border

Created by: JJCoolBean

When nesting a card inside an accordion's card body, the nested card inside the card body of an accordion is missing the bottom border.

• Operating system and version: Windows 7 SP1 64 bit
• Browser and version: Chome 69.0.3497.100
• Reduced test case: https://codepen.io/JJCoolBean/pen/KGraWv